Elegant physicist makes string theory sexy

Alan Boyle Science editor • Profile • E-mail

If you're trying to impress the geeks, being a professional string theorist would have to put you pretty high up on the coolness scale. And if you're a string theorist with books, movies and TV shows to your credit, so much the better.

By those measures, Columbia University physicist Brian Greene has already achieved superstring stardom: His book about string theory, "The Elegant Universe," broke onto bestseller lists and spawned a "Nova" documentary series by the same name (which you can watch online). He has consulted with — and taken cameo roles in — movies ranging from "Frequency" to "Deja Vu" to "The Last Mimzy" (which opens Friday). He's made the talk-show circuit, from "Nightline" and Letterman to "The Colbert Report." And as if all that wasn't enough, he's also organizing a World Science Festival in New York City.

In fact, the biggest knock against Greene is that he's so busy with public outreach that scientists wonder whether he actually has time for string theory. Last year, for example, he was the subject of a meticulously plotted April Fool's joke having to do with a star on the Hollywood Walk of Fame.

Even though less telegenic physicists may turn up their noses, there's no denying that the 44-year-old Greene has managed to make one of physics' most arcane theoretical frontiers a lot sexier. (For the record, Greene is married with a 2-year-old child and another on the way.)

"The Elegant Universe" stoked popular interest in the concept that the fundamental building blocks of reality are tiny vibrating strings — and that such a paradigm could help explain the biggest puzzles of physics. In that role as an explainer of cosmological mysteries, he's following in the footsteps of Cambridge cosmologist Stephen Hawking, author of the similarly bestselling "A Brief History of Time" and occasional TV star.

Greene and Hawking are teaming up for the first time in a double-lecture series on cosmology in Seattle, presented by the Oregon-based Institute for Science, Engineering and Public Policy. Greene takes the stage first, on Monday, and Hawking is due to follow with an April 9 lecture. In a wide-ranging interview with MSNBC.com, Greene previewed his lecture and talked about how he juggles his many roles in science and culture:

MSNBC.com: So how do you feel about sharing a bill with Dr. Hawking?

Greene: Ah, well, it’s quite an honor. He certainly is the towering figure in the field, so I have no problem being the warmup act.

Q: Do you expect your perspectives on cosmology to differ?

A: I suspect that there’s much we agree upon. The place where we may diverge, if at all, is on the most modern developments: the role of string theory in shaping our perspective on cosmology, the possibility of testing string theory and other unified theories through cosmological observations. These are topics that I’ve been putting a lot of effort into and I will be emphasizing in my remarks. I don’t know whether Hawking will refer to any of those developments — nor do I know his views on them.

Q: So you feel as if you might be more optimistic than he might be on the testability of string theory?

A: Actually, Hawking’s quite an optimistic physicist. I’m not sure that I’d be more optimistic. But I think that my emphasis may be somewhat different in that this is the line of research that I personally have been pursuing the last few years.

Q: Can you give a preview of the particulars, because this is a pretty large question. Everyone is looking to the Large Hadron Collider and trying to figure out what specifics they might be looking for to prove string theory is valid.

A: Sure. I think that framing of the question is perfect, because indeed most people do think of the Large Hadron Collider, or accelerators, or atom smashers, or whatever you want to call them, as the primary tools for investigating cutting-edge ideas in particle physics and hopefully in string theory. But there’s another approach that has not received as much attention — which is to try to use astronomical observations to test some of these theories.

The way I like to think about it is, if I have a balloon that has no air in it, and I scribble a message on the outside of that balloon with a very, very fine-tipped pen, you can’t see the message because it’s too small. But then, if the balloon expands, you can take that tiny message, smear it out across this large balloon surface, and now you can easily see it.

It’s our hope that a similar idea might apply to string theory. Strings are very tiny, and that’s what has made them so difficult to test. But perhaps strings leave a little tiny imprint on the young universe, at the time just after the big bang. And then through 14 billion years of cosmic expansion, the universe gets bigger and bigger, and that little tiny imprint of string theory may get smeared out across the sky – just like my little scribble on the balloon gets smeared out across its surface. So the thought is, we may actually be able to test string theory through astronomical observations so long as we know what to look for.

We’ve been doing calculations that suggest that the place to look may be the microwave background radiation. And the thing to look for may be tiny, tiny additional temperature deviations from those that have already been seen, so small that they are a challenge to measure – but it’s not impossible that one day we will. That’s the basic idea.

Q: People have talked about the contribution of the Wilkinson Microwave Anisotropy Probe, and when WMAP’s initial results came out, people may have gotten the impression that those results were the be-all and end-all for study of the cosmic microwave background. But I suppose you’re thinking that there are other missions, such as Planck, that will bring more information to light?

NASA This graph charts data from the Wilkinson Microwave Anisotropy Probe and other studies of the cosmic microwave background, showing several peaks in the data. Careful analysis of "wiggles" in the peaks could reflect the physics of string theory, Greene says.

A: Absolutely. So Planck is one mission, and then there’s CMB-Pol – the polarization measurements. All these experiments have a possibility of giving us more refined data, which will provide a sharper image of just what the universe looked like about 370,000 years after it was born. That kind of precise data has a chance of showing imprints of exotic physics. And among the candidates for that exotic physics, a prime candidate is certainly string theory.

Q: I remember at the time that the WMAP results came out, people were talking about the “second peak” or the “third peak” in the curve showing data about the cosmic microwave background. Is that the sort of thing you’re looking at?

A: That’s part of it. But in fact those features are, from our perspective, the gross overall features. We’re suggesting that on top of those peaks there may be little wiggles. And those little wiggles of a very tiny size could reflect the physics of string theory operating in the early universe. So it’s a difficult measurement, because it was a heroic feat to measure those peaks – now we’re saying hopefully we can go further and measure additional features on top of those.

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